Means for eliminating the effect of polar attraction in electric generators



g- 28, 1962 R. CANTIN 3,051,857

MEANS FOR ELIMINATING THE EFFECT OF POLAR ATTRACTION IN ELECTRIC GENERATORS Filed Feb. 10, 1961 2 Sheets-Sheet 1 IN VEN TOR Roland CANT/N AGENT R. CANTlN I 3 05 1 857 Aug. MEANS FOR ELIMINATING THE EFFECT OF POLAR ATTRACTION IN ELECTRIC GENERATORS Filed Feb. 10, 1961 2 Sheets-Sheet 2 INVENTDR Roland CANT/N AGENT United States Patent 3,051,857 MEANS FOR ELIMINATING THE EFFECT OF POLAR ATTRACTION IN ELECTRIC GEN- ERATORS Roland Cantin, 2193 Tillemont, Montreal, Quebec, Canada Filed Feb. 10, 1961, Ser. No. 88,424 1 Claim. (Cl. 31074) The present invention relates to electric generators or dynamos.

It is known that in dynamo-electric machines having a low member of pole both on the rot r and stator, the resistance to an applied torque is not constant or uniform but varies between a maximum and a minimum depending on those angular positions of the rotor with respect to the stator in which the respective poles are in register and farthest apart respectively. Thus, the torque which must be applied to the shaft of such dynamo-electric machines must have a minimum value at least equal to the torque necessary to overcome the maximum resistance of the rotation of the machine.

It is therefore the general object of the present invention to provide means which considerably decrease the torque required for driving generators for AC. or

DC. current and more especially such generators having a limited number of poles.

Another important object of the present invention resides in the provision of means of the character described which can diminish the required driving torque to about half of the maximum torque normally required.

Another object of the present invention resides in the provision of means of the character described which are of simple construction and relatively inexpensive to manufacture and which may be embodied either as mechanical or elect-ro-magnetic means.

The foregoing and other important objects of the present invention will become more apparent during the following disclosure and by referring to the drawings in which:

FIGURE 1 is a side elevation partially in section of a first embodiment of a generator provided with the means of the present invention;

FIGURE 2 is a cross-section taken through the torque compensating means of the invention;

v FIGURE 3 is an elevation taken from the generator end;

FIGURE 4 is a top plan view partially in plan section of a second embodiment of the invention;

FIGURE 5 is an end section taken along line 55 of FIGURE 4; and

FIGURE 6 is an end section taken along line 6-6 of FIGURE 4.

Referring now more particularly to the drawings in which like reference characters indicate like elements throughout, the device according to the first embodiment is illustrated in FIGURES 1 to 3 inclusive and comprises a base 1 on which is rigidly secured an upstanding ring-like element 2, the side legs of which have bores 3 which are in mutual alignment and are provided with bearings 4 for journaling a horizontally disposed shaft 5, both ends of which project outwardly of ring-like element 2. One outer end of shaft 5 has a threaded portion 6 of enlarged diameter on which is screwed a rotor body 7 of an AC. generator generally indicated at 8. The rotor body 7 is cylindrical and is coaxial with shaft 5. The threaded portion 6 of the latter threadedly engages an axial blind bore of the body 7 and is firmly retained therein by lock nut 9 threaded on portion 6.

A permanent magnet 10 in the shape of a bar is end portions.

tightly fitted within and transversely of the rotor body 7 to form diametrically disposed north and south pole faces 111 and 12 projecting from the peripheral surface of the rotor body 7.

The stator of the generator 8 comprises a solid yoke member 13 rigidly secured to and upstanding from base 1 in the transverse plane of the permanent magnet bar 10; its lateral vertical legs 14 support inwardly directed and axially aligned horizontal pole pieces 15 of laminated construction to prevent the formation of excessive Foucault currents. The people pieces 15 are adapted to register with the pole faces 11 and 12 of the rotor. The pole pieces 15 are surrounded by inductor coils 16, the wires 17 of which are connected in conventional manner in the circuit to be supplied with electricity.

The smaller diameter end 18 of shaft 5 on the opposite side of ring like element 2 is connected to a suitable motive power unit to drive the rotor body 7. Due to the limited number of pole pieces, in the particular case illustrated both the stator and the rotor have two poles, it will be appreciated that the rotor resistance to rotation and consequently the driving torque which has to be exerted on shaft 5 are non-uniform for each complete rotation of the rotor. More particularly, the driving torque is zero when the permanent magnet bar it) is at right angles to the line joining the pole pieces 15 and become negative as the pole faces 11 and 12 approach the pole pieces 15 due to mutual magnetic attraction then increases suddenly as the pole faces 11 and 12 leave and move away from the pole pieces 15. In order to eliminate this variation in the required driving force, means are associated with the generator A, which form the essential feature of the present invention.

In accordance with the first embodiment, these means comprise a cam 19 rigidly secured to shaft 5 in the center of ring like element 2 and disposed transversely of the plane of the latter, said cam 19 being secured in position by means of two lock nuts 20 threadedly engaging the threaded portion 21 of shaft 5 and tightened against the opposite faces of cam 9.

The cam 19 has a generally lozenge shape with diametrically opposed circular portions 22 disp sed on its smaller axis and triangular shaped bosses 23 which are diametrically opposed and disposed on the longer axis of the lozenge figure, said bosses having rounded The bosses 23 are disposed ina plane common with the long axis of the permanent magnet bar 10 of the rotor body 7.

A transversely extending bar 24 is rigidly secured to the top of ring like element 2 in the plane of the cam 19, and levers 25 are pivotally connected at their upper end 26 to the outer ends of bar 24 and are provided at their lower ends with cam follower Wheels 26 mounted on ball bearings and adapted to ride on the periphery of the cam 19. A tension coil spring 27 is connected to the two levers 25 just above the cam follower wheels 26 and urges the two levers one towards the other to bring the wheels 26 in contact with cam 19. The compensating device operates as follows.

When magnet bar 10 is at right angles to the line joining the pole pieces 15, the cam follower wheels 26 ride on the circular portions 22 0f the cam 19; as the pole faces 11 and 12 move towards the pole pieces 15, the cam follower wheels 26 ride on the straight portions of the cam towards the bosses 23 and therefore the levers 25 are caused to move away from each other against the action spring 27. Thus, the attraction between the pole faces 11 and 12 and pole pieces 15 is converted into potential energy within spring 27. As the magnet 10 moves past the pole pieces 15, the wheels 26 will move past the bosses 23 and levers 25 will pivot towards each other so that the spring 27 will release its potential energy in the form of a driving torque exerted on the shaft 5, to thereby help Overcome the resistance to rotation due to the attraction between pole faces 11, 12 and pole pieces 15. Thus, a completely uniform resistance is obtained for all angular positions of the shaft and during a complete revolution and therefore the driving torque required to rotate the rotor is rendered uniform and is much less than the maximum torque required in a generator in which the compensating device of the invention is absent.

Although an A.C. generator arrangement has been illustrated and described, it is understood that the compensating device of the invention can be equally associated with a DC. generator having a limited number of poles.

FIGURES 4 to 6 inclusive illustrate a second embodiment in which the compensating means take the form of permanent magnets. A shaft 30 is journaled in bearings 31 mounted in supports secured to a base 32, one end of the shaft i extended as shown at 33 to be connected to a suitable motive power unit. A cylindrical rotor body 34 is supported by shaft 30 and is coaxial therewith, said rotor body being preferably made of non-ferromagnetic material. The A.C. generator portion 35 of the assembly comprises a permanent magnet bar 36 mounted within rotor body 34 transversely thereof and providing north and south pole faces 37 and 38 projecting outwardly from the peripheral surface of rotor body 34. A first yoke member 39 is rigidly secured to and is upstanding from base 32 and its vertical legs support pole pieces 40 of laminated construction and axially aligned on both sides of the rotor and disposed to register with the permanent magnet bar 36. Inductor coils 41 surround the pole pieces 40 and are connected in parallel to the circuit to be supplied with electricity.

A second yoke member 42 is secured to and is upstanding from base 32 opposite the other end portion of rotor body 34. Said yoke member 42 supports inwardly directed permanent stator magnets 43 having their north pole faces 44 at their inner end and towards the rotor body 34. Two rotor permanent magnets are inserted end to end in a transverse bore made in the rotor body 34 opposite the stator magnet blocks 43. The permanent rotor magnets 45 have their south poles in mutual contact and their north poles projecting outwardly of the rotor body to become in alignment with the north poles of the stator magnets 43. The rotor magnets 45 are in a common plane with the permanent magnet bar 36 of the generator assembly 35 and similarly the stator magnets 43 are in a common plane with the pole pieces 40.

The arrangement of the compensating device produces a counter-attraction relative to the attraction exerted between the permanent magnet bar 36 and the pole pieces 40 of the generator assembly 35; in other words, as the pole faces 37 and 33 approach the pole pieces 40, the attraction produced is counteracted by the repulsion produced between the similar pole faces of the stator and rotor magnets 43 and 45. Thus, potential energy is stored in said blocks 43 and 45. As the bar 36 moves away from the pole pieces 40, the attraction between said elements and the consequent resistance to rotation produced by the generator assembly is counteracted by the repulsion between magnets 43 and 45. Thus a uniform driving torque will drive the generator as in the first embodiment and this driving torque is much less than the maximum torque required for driving a generator without the compensating device of the invention especially when the generator has a limited number of poles.

While preferred embodiments in accordance with the:

present invention have been illustrated and described, it is understood that various modifications may be resorted to without departing from the spirit and scope of the appended claim.

What I claim is:

In combination with an electric generator having a rotor and a stator provided with a limited number of poles angularly spaced apart so that the resistance to rotor rotation is non uniform, means associated with said rotor storing potential energy for portions of rotation of said rotor and converting said potential energy into a driving torque for said rotor for the remaining portions of rotor rotation, said means including rotor permanent magnets having poles of the same kind projectng from said rotor and stator permanent magnets having poles of the same kind coacting with said rotor permanent magnets to produce repulsion of the rotor magnets, said stator magnets being in a plane common with the poles of the stator of the generator.

References Cited in the file of this patent UNITED STATES PATENTS 1,913,948 Perlman June 13, 1933 FOREIGN PATENTS 30,505 Switzerland Apr. 11, 1904 

